The NICHD Human BioSpecimen Repository shall provide the services of storage, monitoring, and distribution for the Maternal and Pediatric Infectious Disease Branch (MPIDB). Required repository services therefore include planning discussions with repository staff to adequately prepare for specimens, receipt of specimens from multiple clinical centers, purchase of freezers to store the specimens, storage of the specimens at the required temperatures; an on-line, searchable inventory system of all specimens, and shipment of biospecimens to analytical labs. The Maternal and Pediatric Infectious Disease Branch (MPIDB) promotes research to investigate the impact of HIV and its treatment on specific populations (pregnant women, infants, children, and adolescents) with the goal of increasing our understanding so we can better combat this infection. There are two main networks supported by the MPIDB that actively collect specimens to be housed in the NICHD repository. These are PHACS (Pediatric HIV AIDS Cohort Study) and IMPMCT (International Maternal Pediatric and Adolescent AIDS Clinical Trials). The Pediatric HIV AIDS Cohort Study (PHACS) is a multicenter United States-based program that follows both perinatally HIV-infected youth and HIV-exposed/uninfected infants, children, and youth. The IMPAACT Network is focused on evaluating potential therapies for HIV infection and its related symptoms in infants, children, adolescents, and pregnant women, including clinical trials of HIV/AIDS interventions for and prevention of mother-to-child transmission. The research agenda includes studies on the pharmacokinetics, safety, optimal dosing, and long-term complications of new antiretroviral (ARV) therapies for HIV/AIDS in pediatric and adolescent populations and in pregnant women. NICHD-funded sites (via Westat contract) utilize the NICHD repository; NIAID-funded sites utilize a separate NIAID-supported repository. NICHD supported sites also perform other trials independently or within other networks. PHACS collects/stores the following types of specimens from the over 3000 participants currently being followed on 3 main protocols and additional substudies: